Automatic telephone system



W. T. POWELL.

AUTOMATIC TELEPHONE SYSTEM. APPLICATION FILED MAR. 2a. 1918.

Patented Apr. 20, 1920.

2 SHEETS-SHEET 1.

pm N a i i //7 van/0r.-

W/hf/eq" I P0 we UNlTED STATES PATENT OFEIQE.

WINFRED T. POWELL, OF EAST ORANGE, NEW' JERSEY, ASSIGNOE TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEVJ YORK, N. Y., A CORPORATION 0F NEW- YORK.

' AUTOMATIC TELEPHONE SYSTEM.

Patented Apr. 20, 1920.

Application filed March 28, 1918. Serial No. 225,219.

To all whom it may concern:

Be it known that I, VVINFRED T. POWELL, a citizen of the United States, residing at East Orange, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a full, clear, concise, and exact description. I

This invention relates to telephone sys tems and more particularly to telephone systems employing automatic switches which are controlled by impulses produced by an impulse transmitting device associated with a calling line. I

In telephone systems employing automatic switches, it sometimes happens that the calling party accidentally opens and closes the calling line circuit momentarily, thereby transmitting impulses which cause the switches of the system to operate in. the same manner as the impulses produced by the proper manipulation of the impulse transmitting device and thus mutilating the connection. a

The object of this invention is to provide means for preventing the operation of a switch by such preliminary accidental impulses.

One feature of this invention is the provision of means for maintaining the stepping relay of the switch disconnected from the line circuit until a certain circuit change has been produced in the calling line circuit.

In accordance with the above mentioned feature a dilferential relay normally has a winding connected in series with each side of the calling line. When the impulse transmitter is moved forward from its normal position, it connects ground to both sides of the line, thereby closing a shunt around one of the windings of the differential relay. The diiierential relay thereupon energizes and causes the stepping relay of the switch to be connected. to the trunk. The windings 01" the dilierential relay are then discon nected from the calling line. If, however, the trunk circuit-switch is opened before the impulse transmitting device is operated, the circuit through both windings of the difi'erential relay is simultaneously opened so that such relay does not energize and cause the stepping relay to be connected to the line.

Other features will appear from the following description and claims. In the drawings, Figure 1 diagrammatically rep resents a portion of a telephone system embodying the features of this invention; and in Fig. 2 an alternative arrangement for ac" complishing the same results is shown.

Referring to Fig. 1, there are shown diagrammatically thercin, a calling subscribers line, a selector circuit, and "a called subscribers line; and Fig. 2 represents a modification of the selector circuit shown in Fig. 1, the dili'erence being that a StQID-EJY-Slii) switch is used in place oi certain relays.

It is' believed that the invention will be bestunderstood by describing the operation of the system disclosed. it will be assumed that the subscriber at substation l desires to establish a connection with substation Then the subscriber at substation l removes his receiver from the switchhoolr; a circuit is completed in the well-known manner to cause the operation of trunk finder or line switch 3 to extend the calling line to an idle trunk leading to a selector switch Upon the seizure of an idle trunk by the brushes of the switch 8, a circuit is established from grounded battery. through the upper winding of differential relay 5, upper winding of relay 6, normal contact 7, upper brush of switch 3, loop at substation 1, middle brush of switch 3, normal contact 8, lower winding of relay 6, lower winding of dili'erential relay 5 to ground. The current flowing through this circuit energizes relay 6, but differential relay 5 is so wound that the flu); produced by one winding neutralizes that of the other so that the relay does not attract it's armatures. Upon the energization of relay 6, a circuit is closed from ground. through armature and contact of relay c, winding of slow-to-release relay 9 to grounded battery. Relay 9 energizes and its uppermost armature and contact, connects ground through conductor 31 to the test brush of the line switch 3 to maintain in the well-known manner such switch open ated. The subscriber at substation 1 proceeds now to operate his impulse transmit ting device 10 to transmit impulses to set the selector switch 4:.

The impulse transmitting device 10 may be any one of the well-known types, modified however. so as to connect ground simultaneously to both sides of the calling line when it is being set. In the present disclosure there is shown a modification of an impulse transmitting device of the wellknown type which is first set by a forward movement of the dial, and then restored to its normal position by a backward movement of the dial. An arm 11 is attached to the dial so that as the dial is moved in its forward direction, which is in the direction indicated by the arrow in the drawing, the arm 11 engages the pivoted lever 12 to connect the contact 13 to ground. When the arm 11 engages the lever 12 during the backward movement of the dial, the lever 12 will be moved away from the contact 13 so that ground will not be connected to it. In addition to the ordinary impulse springs 15, the impulse transmitting device also has an off-normal contact 14 which is closed as soon as the dial leaves its normal position to place a shunt across the telephone line during the transmission of the impulses.

The calling subscriber moves his impulse transmitting device 10 a predetermined distance in the direction of the arrow. As soon as the device leaves its normal position contacts 13 and 14 are closed. A circuit is then closed from grounded battery, through upper winding of differential relay 5, upper winding of relay 6, contact '7, upper brush of line switch 3, impulse springs 15, off-nor mal contact 14, contact 13 to ground; It will thus be observed that the lower winding of differential relay 5 is shunted by this direct ground through the contact 13. Differential relay 5 thereupon energizes and closes a circuit from grounded battery, through winding of relay 19, upper armature and contact of differential relay 5 to ground. Relay 19 energizes and closes a locking circuit for itself from grounded battery, through winding of relay 19, upper armature and contact of relay 19, uppermost armature and contact of slow-to-release relay 9 to ground. Belay 19 also closes a circuit from grounded battery, through winding of relay 18, lower armature and contact of relay 19 to ground. Relay 18 becomes energized and by attracting its armatures disconnects the relays 5 and 6 from the cal ing line and closes a circuit from grounded battery, through the upper winding of stepping relay 16, inner upper armature and back contact of relay 17, upper armature and front contact of relay 18, over the line circuit previously described to ground either through contact'13, or through the switclr hook at substation 1, middle brush of switch 3, inner lower armature and front contact of relay 18, inner lower armature and back contact of relay 1?, and the lower winding of stepping relay 16. The latter circuit is closed as soon as the arm 11 passes by the pivoted member 12. Relay 16 energizes and closes at its armature and front contact a new circuit for relay 9, the original circuit for relay 9 being opened as soon as the relay 6 deenergizes. Since, however, the relay 9 is made slow to release, it maintains its armatures attracted during the changeover. Stepping relay 16 is now connected to the line circuit so as to be operated by each interruption produced therein.

After the calling subscriber has moved the impulse transmitter the desired distance, he releases it, whereupon it is restored to its normal position, and during its restoring movement, short interruptions are produced in linecircuit. Relay 16 thereby becomes intermittently deenergized and energized in accordance with the number of interruptions produced in its circuit. Upon each release of the armature of relay 16, a circuit is closed from grounded battery, through winding of primary magnet 20, winding of slow-to-release relay 21, lower armature and front contact of relay 9, lower armature and back contact of relay 1?, conductor 22, lower armature and contact of relay 18, conductor 23, armature and back contact of relay 16 to ground. Magnet 20 energizes each time this circuit is completed and moves the brushes of the selector switch 4 in a direction to select the desired group of trunks terminating at the selectotr switch 4. Relay 21 also becomes energized in this circuit, but due to its slowness to release, it maintains its armature attracted during the short interruptions produced in this circuit by the vibration of the armature of the stepping relay 16.

As soon as the selector switch leaves its normal position, a circuit is closed from grounded battery, through winding of relay 24, primary oft-normal contact 25, arma ture and front contact of relay 21, inner up per armature and front contact of relay 9 to ground. Relay 24 energizes and closes a locking circuit for itself from grounded battery, through winding of relay 24, primary off-normal contact 25, armature and back contact of magnet 26, inner upper armature and front contact of relay 24 to ground.

After the sending of the first series of i1npulses has ceased, the relay 16 maintains its armatures attracted for a sufficient length of time to allow the relay 21 to deenergize. A cicuit is then closed from grounded battery, through winding of secondary magnet 26, uppermost armature and contact of relay 24, upper armature and back contact of relay 21, inner upper armature and front contact of relay 9 to ground. Magnet 26 energizes and causes the brushes of the selector switch 4 to be moved into engagement with the terminals of a trunk in the selected group. As is well known, the busy or idle condition of such a trunk may be indicated by the connection or the absence of ground at its multiple test terminal. In the present case, the busy condition of a trunk is indicated by the presence of ground on the test terminal thereof.

Magnet 26 by attracting its armature also opens the holding circuit of relay 2th. Relay 24 thereupon denergizes and opens the circuit of the secondary magnet 26, which then de'e'nergizes. If the trunk, with the terminals of which the brushes of the selector switch a: are in engagement at this time, is busy, a circuit is closed from grounded battery, through Winding of relay 241, primary oil'- normal contact 25, armature and back contact of magnet 26, conductor 28, uppermost armature and back contact of relay 17, conductor 27, lowest brush of selector switch l to ground at the connector switch associated with such trunk. Relay 2% then becomes energized and closes the above traced circuit for the secondary magnet 26 to move the brushes of the selector switch l into engagement with the next set of terminals of the selected group. The brushes continue to be moved in a similar manner until they engage an idle set of terminals, the test ter minal of which does not have ground con nected thereto. As soon as the magnet 26 deenergizes after the brushes are moved into engagement with such a set of idle terminals, a circuit iscompleted from grounded battery, through winding of relay 24, pri mary off-normal contact 25, armature and back contact of magnet 26, conductor 28,

-winding of relay l7, conductor 29, uppermost armature and contact of relay 9 to ground. Heretofore, when the circuit for relay as has been closed. the winding of relay 17 has been shunted by the'ground at the test terminal of the busy trunk. The current in the last traced circuit is not sufficient to energize relay 24: but is suflicient to energize relay 17. Since relay 2% does not energize, the magnet 25 remains deenergized and the brushes remain in engagement with the terminals of the idle trunk.

The energization of relay 1? disconnects stepping relay 16 from the calling line, and extends the calling line through the upper brushes of the selector l to the idle switch 30. The deenergization of stepping relay 16 causes in turn the deenergization of relay 9. The slow-to-release relay 9, however, does not de'e'nergize to disconnect ground from the original energizing circuit of relay 17 until after a ground has been connected, in the well-known manner at the connector switch 30, to the test terminal of the seized trunk. A holding circuit for relay 17 is thereupon closed to this ground, through the uppermost armature and front contact of relay 17, conductor 27, and the test brush oi selector switch 4.

The calling subscriber may now control the operation of the connector switch 30 in any well-known manner in order to com plete the connection to the called substation 2.

Upon the termination of the conversation, the calling party by hanging up his receiver causes in the well-known manner the removal of ground from the test terminal of the selector switch 4:. Relay 1? thereupon dee'nergizes and closes a circuit from grounded battery, through winding of release magnet 33, primary oil-normal con-- tact 34, lower armature and back contact of relay 9, lowermost armature and back contact of relay 1?, conductor 22, lowermost armature and front contact of relay 18, con ductor 23, armature and back contact of relay 16 to ground. Under the control of magnet 33, the selector switch a is restored to normal, the circuit of such magnet being opened at primary oil-normal contact Slwhen the switch reaches its normal position. The removal of ground from the test terminal of the selector switch l also causes in the well-known manner the release of the line switch 3.

The modification disclosed in Fig. 2 consists of a step-by-step switch which starts operating after the differential relay is operated and functions to connect the stepping relay to the calling line. This step-by-step switch takes the place of relays 18 and 19 of Fig. 1. i

In the following description, parts in Fig. 2 which correspond to similar parts in Fig. 1, are indicated by the same reference character primed. The talking conductor of the trunk seized by the switch 3 terminates in brushes 35 and 36 of a switch 3? which normally engage terminals to which the relay 6 and differential relay 5 are connected. The stepping magnet 38 of the switch 37 is connected to a third brush of the switch which norn'ially engages a terminal to which the front contact of the ditl erential relay 5 is connected.

It will now be assumed that the line switch 3 has been operated to seize the trunk leading to the selector switch shown in Fig. 2. A circuit is thereupon closed from grounded battery, through the upper winding of difierentia-l relay 5, upper winding of relay 6, upper brush 35 and its normal contact, upper brush and contact of line switch 3 through the calling line circuit, thence through the middle brush and contact of line switch 3, brush 36 and its normal contact, lower winding of relay 6, lower winding of difierential relay 5 to ground. The current flowing in this circuit energizes relay 6 but does not cause relay 5 to attract its armature. The energization of relay 6 closes a circuit from grounded battery, through winding oi slowto-release relay 9, armature and contact of relay 6 to ground. Relay 9 energizes and at its upper armature and contact, connects ground to the test brush of the line switch 3 to maintain such switch operated in the well-known manner.

The calling subscriber now operates his impulse transmitting device to set the selector switch a. As soon as the device leaves its normal position, differential relay 5 is caused to attract its armature in exactly the same manner as relay 5 in Fig. 1. The energization of relay 5 closes acircuit from grounded battery, through winding of stepping magnet 38, armature and back contact of magnet 38, brush and its normal contact, armature and contact of relay 5 to ground. Magnet 38 energizes and moves the brushes 35, 36 and into engagement with their second contacts. Relays 6 and 5 are thereby disconnected from the calling line and relay 16 connected thereto. Relay 16 becomes energized and closes a circuit from grounded battery, through winding of relay d0, left-hand armature and back contact of relay 40, lower armature and front contact of relay 16 to ground. Relay so energizes and closes a locking circuit for itself from grounded battery, through winding of relay 40, left-hand armature and front contact of relay &0, lowest armature and front contact of relay 9 to ground.

lVhen magnet 33 energizes, it opens its own energizing circuit so that it becomes decnergized after its armature has moved far enough to cause the movement of the brushes 35, 36 and 39 on to the next set of terminals. The second contact engaged by brush 39, however, is connected directly to ground so that the magnet 38 is again energized and moves the brushes 35, 36 and 39 into engagement with their third contacts. The magnet 38 continues to be similarly energized and deenergized until the brushes 35, 36 and 39 engage their fifth contacts. The circuit of magnet 38 is opened at such time at the inner lower armature and back contact of relay 9. The brushes 35 and 36 are so arranged that before they disengage a set of contacts, they engage the next succeeding set of contacts. In this way the circuit of stepping relay 16 is not opened by the movement of the brushes of the switch 37 In response to each of the short interruptions produced in the line circuit by the impulse transmitting device of the calling subscriber, the relay l6 deenergizes and closes a circuit from grounded battery through the winding of primary magnet 20, winding of slow-to-release relay 21, right-hand armature and front contact of relay d0, inner lower armature and front contact of relay 9, lowest arnnture and back contact of relay 17, lower armature and back contact of stepping relay 16 to ground.

Since the operation of the circuit of Fig. 2 from this point is substantially similar to that described in connection with Fig. 1, it is believed that further description is unnecessary of the manner in which the brushes of the switch l are moved into engagement with an idle trunk leading to a connector switch.

Upon the termination of the conversation, the relay 1? is deenergized in the wellknown manner and completes acircuit from grounded battery, through winding of magnet 38, armature and back contact of magnet 38, .brush 39 and its fifth contact, inner lower armature and back contact of relay 9, lower armature and back contact of relay 17, lower armature and back contact of relay 16 to ground. Magnet 38 energizes and moves the brushes 35, 36 and 39 into engagement with the normal contacts of the trunk with which it is associated. The release of the other switches used in establishing the connection takes place in the well-known manner.

From the foregoing description it will be observed that stepping relay is normally disconnected from the calling line until a particular circuit change is produced in the line circuit. Therefore any preliminary impulses in the line circuit which occur before this particular circuit change takes place, do not operate the stepping relay to set the switch upon the wrong line.

What is claimed is:

1. In a telephone system, a switch, a calling line, conductors at said switch to which said calling line may be connected, means for initiating a call on said line, means for establishing a connection between said line and said conductors, means for transmitting impulses over said conductors, a stepping relay at said switch normally disconnected from said conductors, and means controlled by said calling line independently of said call -initiating means for connecting said stepping relay to said conductors.

2. In a telephone system, a switch, a calling line, means for initiating a call on said line, means for extending said calling line to said switch, means for producing impulses in said calling line, impulse receiving means at said switch arranged to be controlled by said impulses to control the operation of said switch, means under the control of the calling line after said calling line is extended to said switch for connecting said impulse receiving means to said calling line, and means independent of said callinitiating means for actuating said connectmg means.

3. In a telephone system, a switch, a pair of conductors terminating at said switch.

a differential relay normally connected in series with both conductors, a stepping relay for said switch normally disconnected from said conductors, and means controlled by said differential relay for connecting said stepping relay to said conductors.

l. In a telephone system, a switch, a pair of conductors terminating at said switch, a differential relay normally connected in series with both conductors, a stepping relay for said switch normally disconnected from said conductors, and means controlled by said differential relay for connecting said stepping relay to said conductors and for disconnecting said differential relay from said conductors.

5. In a telephone system, a switch, a calling line, a pair of conductors for connecting said calling line to said switch, means for transmitting impulses over said conductors, impulse receiving means at said switch arranged to be operated by said impulses to control the operation of said switch, said impulse receiving means being normally disconnected from said conductors, a differential relay normally connected to said conductors, and means controlled by said differential relay for connecting said impulse receiving means to said conductors.

6. In a telephone system, a switch, a calling line, a pair of conductors for connecting said calling line to said switch, means for t ansmitting impulses over said conductors, impulse receiving means at said switch arranged to be operated by said impulses to control the operation of said switch, said impulse receiving means being normally disconnected from said conductors, a differential relay normally connected to said conductors, and means controlled by said call ing line for operating said differential relay, and means controlled by said differential relay for connecting said impulse receiving means to said conductors.

7. In a telephone system, a switch, a calling line, conductors for connecting said line to said switch, an impulse transmitter for transmitting impulses over said conductors, a stepping relay at said switch arranged to be operated by impulses transmitted over said conductors, said relay being normally disconnected from said conductors, and means at said switch controlled by operation of said impulse transmitter for connecting said stepping relay to said conductors.

8. In a telephone system, a switch, a calling line, conductors for connecting said line to said switch, an impulse transmitter for transmitting impulses over said conductors, a stepping relay at said switch arranged to be operated by impulses transmitted over said conductors, said relay being normally disconnected from said conductors, a differential relay at said switch connected to said conductors, and means operated by the operation of said impulse transmitter for operating said differential relay to connect said stepping relay to said conductors.

9. In a telephone system, a switch, an incoming line terminating at said switch, means for producing circuit changes of different characters in said incoming line, a stepping relay for said switch responsive to circuit changes of a certain character in said incoming line, said relay being normally disconnected from said line, and means operated by a circuit change of a particular character produced in said incoming line for connecting said stepping relay in said incoming line, such circuit change being of a diterent character than that which operates said stepping relay.

10. In a telephone system, a switch, an incoming line terminating at said switch, means for producing interruptions in said incoming line, means for producing a circuit change of a different character in said incoming line, a stepping relay for said switch responsive to said circuit interruptions, said relay being normally disconnected from said line, and means operated by said circuit change of a different character for connecting said stepping relay to said incoming line.

11. In a telephone system a switch, an incoming line terminating at said switch, means for producing interruptions in said incoming line, means for connecting ground simultaneously to the conductors of said line, a stepping relay for said switch responsive to said circuit interruptions, said relay being normally disconnected from said line, and means operated by the connection of said ground to the conductors of said line for connecting said stepping relay to said conductors of said incoming line.

12. In a telephone system, a switch. an incoming line terminating at said switch, means for producing interruptions in said incoming line, means for connecting ground simultaneously to the conductors of said line, a stepping relay for said switch responsive to said circuit interruptions, a differential relay ,normally connected to said incoming line, said relay being operated by the connection of ground to the conductors of said line, and means controlled by said differential relay for con necting said impulse relay to said incoming line.

In witness whereof. I hereunto subscribe my name this 21st day of March, A. I). 1918.

VVINFRED T. POWELL. 

